1. Field of the Invention
The invention relates to a method for producing a cross-linked elastomer in which a mixture is produced comprising at least one latex and at least one starter component for initiating the cross-linking reaction or a latex that has at least one starter component or starter group in the molecule, in particular in liquid phase, a method for producing a latex product with a predetermined form in which at least one latex is cross-linked and the molding is carried out before or after the cross-linking, a method for producing a dipped article from at least one latex, in particular a glove or a condom, in which a mold in an outer contour that corresponds to the dipped article to be produced is dipped for a predetermined time into a dipping bath containing a mixture with the at least one latex, optionally after dipping in another dipping bath with a coagulating agent, and subsequently the dipped article is solidified and/or dried, optionally after a postcure, a mixture for producing a latex product, comprising at least one latex and at least one starter component for initiating a cross-linking reaction, and optionally further auxiliaries, a mixture for producing a dipped article from at least one latex, in particular a glove or a condom, a glove produced from an elastomer cross-linked with a starter component, formed by elastomer molecules, a device for producing a cross-linked elastomer with a reactor in which a mixture comprising at least one latex and at least one starter component for initiating the cross-linking reaction can be filled, and optionally with at least one circulating device for the mixture, and the use of the mixture according to the invention.
2. Prior Art
In order to give elastomers the specific elastic properties, the polymer chains of the elastomer have to be at least partially cross-linked with one another. The cross-linking generally takes place via double bonds that are either in the main chain, such as, e.g., with polyisoprene, polybutadiene, styrene-butadiene rubber, chloroprene, nitrile-butadiene rubber, or a side chain, such as, e.g., with EPDM, of the elastomer. On an industrial scale the cross-linking of elastomers, including rubber latex, has hitherto been carried out in three different ways.
The most widespread is the cross-linking, i.e., vulcanization, of elastomers by means of molecular sulfur, which dates back to Goodyear. Since vulcanization with sulfur alone entails reaction times that are too long, vulcanization accelerators are added. These are organosulfur compounds, such as dithiocarbamate, mercaptobenzothiazole or xanthogenate. Since the cross-linking of rubber lattices or rubber copolymers has to be carried out at low temperatures so as not to destabilize the latex, the use of very reactive vulcanization accelerators is essential.
Another way of cross-linking elastomers is the reaction with organic peroxides. Compounds, such as dicumyl peroxide or dibenzoyl peroxide, are thereby thermally split into radicals which initiate the cross-linking of the elastomer chains. It is thereby advantageous if work is carried out with the exclusion of air, since peroxides are oxygen-sensitive, which is why the cross-linking is often carried out in molten salt baths.
In addition to the thermal cross-linking methods there are also radiation cross-linking methods in which energetic electron radiation or gamma radiation is used. In these methods additional reagents, such as, e.g., acrylates, are often added to the rubber latex to be cross-linked. A radiation cross-linking method of this type is known, e.g., from U.S. Pat. No. 6,329,444 B. This document describes in particular a medical glove comprising cis-1,4-polyisoprene, whereby this synthetic rubber has the advantage that compared to natural rubber it is protein-free and sulfur-free. This medical glove is made by dip-molding of a prevulcanized cis-1,4-polyisoprene. The prevulcanization or vulcanization is carried out, as mentioned above, by means of electron radiation or gamma radiation without chemical sensitizers. Doses of 20 megarad to 40 megarad are thereby used. Peroxide cross-linking is also described in this US-B1.